Examples of known molding systems are (amongst others): (i) the HyPET™ Molding System, (ii) the Quadloc™ Molding System, (iii) the Hylectric™ Molding System, and (iv) the HyMet™ Molding System, all manufactured by Husky Injection Molding Systems Limited (Location: Bolton, Ontario, Canada; www.husky.ca). Molding systems, such as the ones listed above typically use hydraulic systems to power various subsystems, such as stroke and clamp actuators, and injection screws and pistons. A pump drives hydraulic fluid through the system.
FIG. 1 is a simplified plan view of a generic molding system 20 (for example, an injection molding system hereafter referred to as the “system 20”). The system 20 is used to mold one or more molded articles (not shown). The system 20 includes components that are known to persons skilled in the art and these known components will not be described here; these known components are described, by way of example, in the following references: (i) Injection Molding Handbook by Osswald/Turng/Gramann ISBN: 3-446-21669-2; publisher: Hanser, and (ii) Injection Molding Handbook by Rosato and Rosato ISBN: 0-412-99381-3; publisher: Chapman & Hill. The system 20 includes (amongst other things): an injection-type extruder 22 (hereafter referred to as the “extruder 22”) and a clamping assembly 23.
The extruder 22 includes a hopper 24, a human-machine interface, hereafter referred to as the “HMI 28”. The extruder 22 has a barrel and a reciprocating screw 26 disposed in the barrel. Alternatively, the extruder 22 could be a two stage shooting pot configuration. The hopper 24 is coupled to a feed throat of the extruder 22 so as to deliver pellets of moldable material to the extruder 22. The extruder 22 is configured to: (i) process the pellets into an injectable molding material, and (ii) inject the injectable material into a mold that is held closed by the platens 30, 32 after the platens 30, 32 have been stroked together. The HMI 28 is coupled to the control equipment, and the HMI 28 is used to assist an operator in monitoring and controlling operations of the system 20.
The clamping assembly 23 includes a stationary platen 30, and a moveable platen 32. Referring now to FIG. 2, a clamping assembly 23 manufactured by the applicant is shown in greater detail. The stationary platen 30 is configured to support a stationary mold portion 31a of a mold 31. The moveable platen 32 is configured to: (i) support a moveable mold portion 31b of the mold 31, and (ii) move relative to the stationary platen 30 so that the mold portions of the mold 31 may be separated from each other or closed together. A mold stroke actuator 36 (hereafter referred to as the “actuator 36”) is coupled to the movable platen 32 and a clamp platen 35. The mold stroke actuator 36 is used to stroke the moveable platen 32 relative to the stationary platen 30. In the presently-illustrated embodiment, the actuator 36 is a hydraulic piston. Typically, during mold closure, the actuator 36 decelerates shortly before achieving contact between the two mold halves to reduce the impact and preserve the lifespan of the mold. The clamp platen 35 further supports a clamp actuator 38 coaxially located around the mold stroke actuator 36. Four tie bars 40 each extend between clamp platen 35 and stationary platen 30.
Movement of movable platen 32 is regulated by a predetermined desired velocity profile, which is generated based on operator inputs of acceleration, maximum speed, deceleration and stroke distance through HMI 28, or alternatively, is provided by a lookup table. For every moment of the actuator stroke cycle, a closing velocity setpoint is provided for movable platen 32. Thus, at T=0 the velocity setpoint starts at zero. The velocity setpoint reaches the peak and then begins decelerating to avoid the mold halves from crashing together. Open or closed loop control is used to regulate the actual acceleration and deceleration, based on either time or position.
U.S. Pat. No. 5,238,383 to Bannai teaches a mold opening controller for injection molding machines, having a control unit for controlling the hydraulic circuit. The control unit having a setter for setting acceleration/deceleration functions of a movable portion such as the movable mold; a data input for the setter; an operational unit for calculating the acceleration/deceleration of portions of the movable mold and the acceleration/deceleration speeds at each moving position at the time of the acceleration/deceleration on the bases of data from the setter and the data input; a position sensor for detecting the moving position of the movable mold; and a control for controlling the hydraulic circuit so that acceleration/deceleration positions of the movable mold and its moving speed at each position correspond to the output values of the operational unit through the position sensor.
US patent application 2007/0182044A1 to Grimm teaches a method for operating an injection molding machine, particularly a method for securing tools of an injection molding machine, a desired variable curve is determined along at least one section of a travel path of a molding tool in a desired variable determination phase, and the injection molding machine is operated according to the determined desired variable curve in a subsequent operational phase. A default curve of at least one initial variable is predefined, the molding tool is driven in accordance with the default curve of the initial variable in a test run, at least one resulting value of the desired variable is measured and stored during the test run, and a desired variable curve is formed along the section of the travel path from the measured values of the desired variable.